CRM018B Dehydrated Culture Medium 500g/bottle

Intended Use

For the rapid detection of Escherichia coli in food samples.

Principle and Interpretation

Tryptone provides nitrogen sources, vitamins, and growth factors.5-Bromo-4-chloro-3-indolyl-β-D-glucuronide (BCIG) acts as a chromogenic substrate. Escherichia coli β-glucuronidase hydrolyzes BCIG, releasing a chromogen that produces blue-green colonies. Bile Salt No.3 inhibits Gram-positive bacteria, particularly Gram-positive bacilli and Enterococcus faecalis. Agar serves as the solidifying agent.

Formulation

Ingredients	/liter
Tryptone	20.0g
Bile Salt No. 3	1.5g
5-Bromo-4-chloro-3-indolyl-β-D-glucuronide (BCIG)	0.075g
Agar	13.0g
pH 7.2±0.2 at 25°C

Preparation

Weigh 34.6 g of the dry powder and add to 1 L of distilled or purified water. Stir and heat to boiling until fully dissolved. Autoclave at 121°C for 15 minutes, then cool to 50°C.Pour into sterile Petri dishes.

Quality Control

Cultural characteristics observed after incubation at 35-37°C for 24 hours

Quality control strains	Approx. Inoculum(CFU)	Recovery	Characteristics
Escherichia coli ATCC 25922	10-100	PR≥0.7	Blue-green colonies
Escherichia coli CMCC(B)44102	> 104	PR≥0.7	Blue-green colonies
Citrobacter freundii ATCC 43864	> 104	Growth observed	White colonies
Enterococcus faecalis ATCC 29212	> 104	G ≤1	No growth

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Storage and Shelf Life

2-30°C，Keep container tightly closed, avoid direct sunlight. Use before expiry date on the label.

Precautions

1. When weighing the dehydrated medium, please wear masks to avoid causing respiratory system discomfort 2. Keep container tightly closed after using to prevent clumping.

Waste Disposal

Microbiological contamination was disposed by autoclaving at 121°C for 30 minutes.

Revision

On June 14, 2024

Escherichia coli: Blue-green colonies
Other bacteria: White colonies or inhibited/no growth